This invention relates to an improved process for accelerating the cure rate of thermoplastic blends of polyolefins and ethylene-containing terpolymers.
Blends of plastics, for example, crystalline polypropylene, and ethylene/alkyl acrylate/glycidyl methacrylate terpolymers have been dynamically cured with polycarboxylic acids, such as adipic acid. Such cures produce thermoplastic compositions having excellent physical properties, however, the cure rate is very slow and, therefore, the process is economically unattractive due to the unduly long cure rates. It is also known that stannous octoate functions as a curative for the ethylene-containing terpolymers of the thermoplastic compositions described above and the rate of cure of the thermoplastic composition is fast. However, the physical properties, including tensile strength and compression set, are substantially detrimentally affected and, therefore, the usefulness of the composition is limited. There has been a need to increase the cure rate of the thermoplastic composition to make the process commercially attractive while, at the same time, maintaining the excellent physical properties of the composition obtained with curatives, such as adipic acid, that require rather excessive time periods for adequate cure.